Magnetic disk devices tend to increase in memory density and capacity every year, and are expected to be used in many applications other than just as large external memory devices added to a conventional general computer system or personal computer. For example, proposed uses for a magnetic disk device include mounting it in a portable small-sized information processing apparatus, which allows a user to carry necessary data recorded in the magnetic disk device outdoors.
If a magnetic disk device is to be mounted in a portable small-sized information processing apparatus, however, it is essential to make the magnetic disk device small and thin. In this regard, the goal of magnetic disk device design is aimed at reducing the size of the device so that it satisfies a size (thickness: 5 mm or less) requirement of a so-called PC card specification of PCMCIA (Personal Computer Memory Card International Association)/JEIDA (Japan Electronic Industry Development Association) and the like. A variety of mechanisms have been disclosed for satisfying such a device thickness of 5 mm or less in a magnetic disk device using a small diameter disk having a diameter of 1.8 inch.
For example, International Publication No. W093/10535 discloses a thin magnetic disk device having a device thickness of 5 mm that is intended to be realized by holding a 1.8 inch disk between electronic parts mounted between printed circuit boards and the inner surfaces of a housing and a cover. In this technique, the electronic parts are mounted on a thin printed circuit board rather than a conventional thick one, and they are arranged on both sides of a thin disk having a relatively large space in the thickness direction, to thus make thin the total thickness of the device. This technique also adopts a spindle motor structure wherein two ball bearings can be mounted in a small inside diameter (12 mm) portion of the 1.8 inch disk along the spindle axis and also a magnet rotor that can be contained in a hub of the disk by the effect of using a face-to-face spindle motor, to thus achieve a magnetic disk device.
In Japanese Patent Laid-open No. Hei 6-84302, a thin actuator is disclosed that is intended to be realized by axially stacking and clamping a so-called guide arm integrated type suspension in which a suspension mounting a magnetic disk/slider is welded to a guide arm, a coil holder for supporting a coil and a spacer, around a sleeve of a pivot bearing of an actuator. The guide arm integrated type suspension is made thin by welding a suspension mounting a magnetic head to a thin guide arm.
At present, the supporting of a suspension on a guide arm is generally performed by welding a cylindrical member to an end portion of the suspension, inserting the cylindrical member of the suspension in a hole provided at the leading end of the guide arm, and fastening the hole by caulking. In this case, a so-called integrated carriage integrating a plurality of the guide arms is generally used. In the method of fastening the suspension to the guide arm, the suspension is inevitably required to be relatively thick for obtaining a practical holding force. Consequently, the technique disclosed in Japanese Patent Laid-open No. Hei 6-84302 in which a suspension only has a thickness sufficient to be welded to a guide arm is advantageous for making a thin suspension.
Incidentally, a housing and cover containing a magnetic disk is required to be sealed for realizing a highly reliable magnetic disk device. In a technique disclosed in U.S. Pat. No. 5,276,577/Japanese Patent Laid-open No. Hei 6-215554, the sealing performance at a mating portion between the housing and the cover and at an extension portion of the FPCs (flexible printed circuit board), a gap is formed that is simply covered using a tape seal having a constant width. on the other hand, as disclosed in Japanese Patent Laid-open No. Sho 62-279587, a packing is held between a flat housing and a cover, to maintain the sealed housing area.